Project Summary: Our broad goals are to characterize the identity, developmental timecourse, and relative plasticity (modifiability/vulnerability) of neural systems and subsystems important in language processing and in attentional and sensory skills that are central to language. In children ages 3-17, we will acquire behavioral data, event-related brain potentials (ERPs), and, in the 6-17 year olds, structural and functional magnetic resonance images (fMRI) of the brain to characterize both the timing and the location of neural activity as participants perform tasks designed to manipulate specific aspects of sensory, attentional, and language processing. We will test the hypotheses that (1) systems important in semantic processing mature earlier than those important in grammatical and phonological processing, and that (2) longer developing systems are less mature in lower compared to higher SES children. In view of the central role of auditory attention and rapid auditory processing in language skills, we will also assess the hypotheses that (3) some aspects of the neural mechanisms underlying focused auditory attention are not mature until at least 10 years of age and (4) these systems are less mature in lower than higher SES children. We will also assess the hypotheses that (5) the systems important for rapid auditory processing develop slowly and (6) may be less mature in lower than higher SES children. We will test the hypotheses that (1) the same duration of exposure to English as a second language results in more typical language and related, brain systems at 3-5 years than at 6-8 years, (2) lower SES ESL children have less mature attentional systems than higher SES ESL children, and (3) lower SES ESL children have lower proficiency English language skills, and the related brain systems are less mature. In a third series of experiments we will assess the relative modifiability of these systems by comparing brain organization and behavior of monolingual children aged 3-5 years before and after 8 weeks of a small group intervention focusing on training language or attentional skills. We will test the hypothesis that increased language and cognitive input will lead to increases in semantic, grammatical, phonological, and attentional skills and related neural systems. Relevance: Since the proposed research will provide evidence about which cognitive and language skills and related brain systems are most altered by environmental input, these studies will contribute information of practical significance for the development, evaluation, and refinement of educational and intervention programs for typically developing, at-risk, and ESL children.